Currently, the cores on magnetic assemblies having a combination of an extended E-core and an I-core are held together with tape or glue. The two cores must be held in place during assembly until the tape is secured or until the glue is dried. Adding tape or glue to restrain the cores requires additional steps during an assembly process and adds cost to the manufacturing process. Accordingly, a need exists for a low-cost bobbin and core assembly method for a combination of an E-core and an I-core that does not require taping or gluing the cores together.